Enable libkms by default on DragonFly

Signed-off-by: François Tigeot <ftigeot@wolfpond.org>
diff --git a/configure.ac b/configure.ac
index d2d19d6..b7eef96 100644
--- a/configure.ac
+++ b/configure.ac
@@ -187,6 +187,7 @@
 		linux*)		LIBKMS="yes" ;;
 		freebsd* | kfreebsd*-gnu)
 				LIBKMS="yes" ;;
+		dragonfly*)	LIBKMS="yes" ;;
 		*)		LIBKMS="no" ;;
 	esac
 fi